Intraocular Pressure Control after Extraocular Muscle Surgery in Graves' Orbitopathy with Myopathy and Secondary Glaucoma

Wai Ho Chan

Purpose: To evaluate the intraocular pressure (IOP) control in subjects with thyroid-associated myopathy and secondary glaucoma after extraocular muscle surgery.

Method: The medical records of 11 subjects in a regional hospital of Hong Kong during 2006 – 2009 with thyroid-associated myopathy and secondary glaucoma with extraocular muscle surgery done were reviewed. Patients with unstable thyroid status, previous orbital surgery and radiotherapy done were excluded.

Result: Eleven subjects (3 male and 8 female) were identified with mean age of 48.5 years (range, 32 - 66). Isolated hypotropia is the commonest (54.5%) followed by combined hypotropia and esotropia (27.2%). All patients have diplopia resolved and nine patients (81.8%) have postoperative residual deviation within 5 PD. Preoperative all patients needed 1 – 3 types of anti-glaucoma eyedrops with average 2.1 (range 1 -3). Four patients were operated mainly due to inadequate IOP controlled by three types of anti-glaucoma eyedrops. Postoperative reduction of intraocular pressure was seen in all cases with decreased the amount of anti-glaucoma eyedrops to ≤ 1 (average 0.91).

Conclusion: The mechanism of the raised IOP in thyroid ophthalmolopathy may be due to a variety of mechanisms: elevated episcleral venous pressure, contraction of extraocular muscles, chronic exposure leading to chronic inflammation and increased mucopolysaccharide deposition within the outflow system. Our result shows that in the selected subgroup of subjects with thyroid-associated myopathy and glaucoma, extraocular muscle surgery in addition to relieve diplopia can also result in a significantly reduction in IOP and better control of glaucoma.